Graphene: critical mass - scaling up production

Materials World magazine

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26 Nov 2013

US-based Lockheed Martin has patented a graphene membrane for water filtration, but plans for scale-up are still unconfirmed. Meanwhile, the UK is still years away from bulk production. Ledetta Asfa-Wossen reports.

It’s that old chestnut, how do you translate two Nobel prizes into high value-added manufacturing? Professor Andrea Ferrari, Head of the Graphene Centre at the University of Cambridge, UK, laid down a few home truths at the HVM Graphene event. ‘The 2010 Nobel prize was awarded for the physics behind the material, [not its manufacture]’. Ferrari added that while early graphite production methods date back to 1896, graphene was only proposed as a material in 1947 and not fully explored until 2004. But even so, he said the UK needs to step up focus on end products. ‘All the touchscreens in the world probably amount to 10kg of graphene. The material costs nothing. The money to be made is from the product.’

The most commercially feasible types of graphene were noted to come in three forms – as an oxide, monolayer film or graphene nanoplatelets (GNP). The material’s strength and flexibility, due to its high Young modulus (220kgm-3) and tensile strength (~130GPa), make it an ideal candidate for flexible electronics, MEMS resonators and sensors. Dr Richard van Rijn, of University of Cambridge spin-off Applied Nanolayers (AN), explained, ‘Graphene electrons have high electron mobility that is fit for a host of chip and transistor technologies where graphene can replace or be added to silicon. High thermal conductivity (5,000Wm-1K-1) also makes it a heat sink for electronic circuits.’

Of growing importance, added Rijn, is the use of graphene as a transparent conductor, to replace indium tin oxide in touchscreens. Another R&D area that is seeing growth is optical applications as graphene-based lasers, where around 2.3% absorption of white light can be absorbed through a single layer. To take advantage of these unique properties, AN is conducting a project that will produce CVD wafer production lines for graphene in the Netherlands. The company is also studying the growth of graphene on rhodium.

At the grain boundary
However, Rijn noted that while the list of potential applications is endless, so are the challenges to manufacturing the material. The largest challenge, said Rijn, has been quality control. ‘A robust quality analysis chain is needed to understand the manufacturing of graphene in full. Raman spectroscopy is a useful tool, but we need many more analysis methods to understand the material. Grain boundaries are a problem. You need to measure resistance along it, as it alters sheet resistance.’

Other challenges include controlling the number of layers in the material, domain size, and substrate and graphene morphology. The high cost of transfer methods of graphene onto a substrate were also discussed. Rijn stated that one answer could be an electrochemical delamination technique that requires no etching or use of expensive metal substrates such as copper.

Dr Patrick Frantz, CEO of Cambridge Graphene Platform, UK, talked of developments in graphene for 2D inks in UHF RFID. ‘At the moment, we can’t even produce enough graphene ink, but that is mainly due to manpower and growing demand from buyers in Asia. Graphene ink has no chemical contamination, high monolayer flake yield (up to 70%), and is a low-cost alternative to silver or laser-sintered copper ink. In the future, graphene will probably be used more as an additive rather than a complete solution, to enhance other inks,’ added Frantz.

How soon is now?
One question that was regurgitated by delegates and spat back out to the panel, was, ‘What will the first real graphene product be in the UK?’ After a long pause, Dr Steve Thomas of Conductive Ink Ltd suggested OLED technology. But Dr Nathan Hill, of the National Graphene Institute (NGI) currently being built in Manchester, added that OLED products were still years away. Meanwhile, Professor Richard Palmer of Birmingham University, UK, placed his bet on pharmaceutical catalysts. But aside from firming up applications, Thomas said researchers need to look further into the failures of graphene to encourage commercialisation. ‘R&D can be too focused on the benefits. The first thing a customer will do is try to break the product. We need to be prepared. If you give a customer a copper transistor, they’ll put it into a salt mist and say it corroded.’

The issue of intellectual property (IP) was also raised as a restricting factor among the afternoon panel, which noted that IP must not be too financially demanding. While companies such as Samsung can cover their costs, SMEs will be forced to migrate their innovations.

Manchester leads the way
Dr Kryzstof Koziol of Cambridge Nanosystems Ltd stated that the main hindrance to bulk production has been investment and commitment, although Hill disagreed, mentioning three major industry projects that are underway. The Graphene-based Electroresponsive Hydrogels project, led by the University of Manchester, has so far trialled drug-carrier graphene gels and found that while there was significant inflammation in multiwalled nanotube hybrid and blank gels due to heating, graphene gels remained intact.

Hill added that, with the ultracapacitor market forecast to reach US$3.5bln by 2020, the NGI is also leading an electrochemical energy storage project with electronics producer SHARP to explore the benefits of graphene in electrochemical devices. The aim is to create low-cost processes that will surpass the current bottleneck in batteries (103Wkg-1) and supercapacitors (3–5Whkg-1). Another project involving NGI and Crown Packaging is looking at graphene-based membranes for barrier materials in food packaging. The initiative will involve more than 14 companies, but ‘industry needs to see graphene as a 15-year game. Nothing happens overnight,’ said Hill. ‘I think we’re beyond the hype stage, but 10 years on, the bridge is too wide. Companies want clear applications and their standardisation and environmental concerns addressed. The rate of R&D is one high-quality paper a week in Manchester and two for the UK overall.’ But there is a lot more work to be done. As Hill said, ‘Graphene at Manchester is great, but graphene in the UK would be greater still’.